Durable anti-crack fiber mortar and preparation method thereof

Abstract

The invention relates to the technical field of mortar, in particular to durable anti-crack fiber mortar and a preparation method thereof. The durable anti-cracking fiber mortar is prepared from the following raw materials in parts by mass: 80 to 120 parts of cement, 60 to 80 parts of sand, 30 to 50 parts of coarse aggregate, 10 to 20 parts of composite cellulose aerogel, 1 to 5 parts of ultra-high molecular weight polyethylene fiber, 4.5 to 7.5 parts of polymer powder, 1.5 to 2.5 parts of ethyl acrylate emulsion, 1 to 2 parts of sodium tripolyphosphate, 1 to 5 parts of silica sol particles, 1 to 2 parts of defoaming agent, 1 to 2 parts of water reducing agent and 80 to 160 parts of water, the composite cellulose aerogel comprises the following raw materials: cellulose nanofibers and graphene oxide, wherein the mass ratio of the cellulose nanofibers to the graphene oxide is (1-5): (1-2). The mechanical property of the mortar is effectively improved, the freezing resistance and durability are excellent, and the comprehensive performance is good.

Description

Technical Field

[0001] The present invention relates to the technical field of mortar, and in particular to a durable crack-resistant fiber mortar and a preparation method thereof. Background Art

[0002] Mortar is a material widely used in hydraulic engineering and civil engineering, playing a key role in engineering construction. Mortar is prepared by mixing inorganic binders, fine aggregates and water in proportion, also known as grout, and is used for masonry and plastering works. Ordinary mortar materials are prepared by adding fibrous reinforcing materials to gypsum, lime paste or clay and adding water to form a paste, which is called ash, paste, mud or mastic.

[0003] With the development of society, the strength requirements for cement and cement-based materials are getting higher and higher. People have begun to continuously study adding various substances to cement mortar to enhance its toughness and adhesion. At present, there are common cracking situations in the use of concrete for tunnel lining in China, a large number of buildings have durability problems, and the collapse accidents of concrete structure buildings occur frequently.

[0004] At present, the most widely used method is to modify mortar with polymers prepared by emulsion polymerization to improve the durability of mortar. However, most mortars have problems such as poor frost resistance and easy cracking, which seriously affect the construction quality. Summary of the Invention

[0005] The purpose of the present invention is to solve the disadvantages existing in the prior art, and to provide a durable crack-resistant fiber mortar and a preparation method thereof.

[0006] A durable crack-resistant fiber mortar, the raw materials of which by mass include: 80-120 parts of cement, 60-80 parts of sand, 30-50 parts of coarse aggregate, 10-20 parts of composite cellulose aerogel, 1-5 parts of ultra-high molecular weight polyethylene fiber, 4.5-7.5 parts of polymer powder, 1.5-2.5 parts of ethyl acrylate emulsion, 1-2 parts of sodium tripolyphosphate, 1-5 parts of silica sol particles, 1-2 parts of defoamer, 1-2 parts of water reducer, 80-160 parts of water; the raw materials of the composite cellulose aerogel include: cellulose nanofibers, graphene oxide, and the mass ratio of cellulose nanofibers to graphene oxide is 1-5:1-2.

[0007] Preferably, the cement is P.O.42.5 Portland cement or / and P.O.52.5 Portland cement.

[0008] Preferably, the polymer powder is redispersible latex powder.

[0009] Preferably, the fineness modulus of the sand is 2.0-2.5.

[0010] Preferably, the water reducer includes: polycarboxylate water reducer and melamine water reducer.

[0011] Preferably, the mass ratio of the polycarboxylate water reducer to the melamine water reducer is 3 - 5:1.

[0012] Preferably, the composite cellulose aerogel is prepared by the following specific operations: adding cellulose nanofibers and graphene oxide into water, ultrasonic treatment for 1 - 2 h, adding acetic acid solution and continuing ultrasonic treatment for 10 - 20 min, standing for 5 - 10 h, and then freeze spinning in an ethanol bath and freeze drying.

[0013] More preferably, the concentration of the acetic acid solution is 1 - 2 mol / L.

[0014] More preferably, the ultrasonic frequency is 20 - 30 kHz.

[0015] More preferably, the inner diameter of the spinning needle is 800 - 1000 μm.

[0016] The preparation method of the above durable crack - resistant fiber mortar includes the following steps:

[0017] S1. Stir the composite cellulose aerogel, ultra - high molecular weight polyethylene fiber, and polymer powder for 10 - 20 min to obtain premix a;

[0018] S2. Stir cement, sand, coarse aggregate, ethyl acrylate emulsion, sodium tripolyphosphate, silica sol particles, defoamer, water reducer, and water for 10 - 30 min to obtain premix b;

[0019] S3. Mix premix a and premix b evenly.

[0020] Beneficial effects:

[0021] In the present invention, the cellulose nanofibers and graphene oxide are compounded. With the cooperation of acetic acid, the combination stability of the two is extremely good. During the freezing process, a porous three - dimensional network structure is formed by the ice crystal template method, which not only has the characteristics of controllable pore size and orderly pore arrangement, but also can rebound after being compressed, with good elasticity. At the same time, it is compounded with polymer powder, which can significantly reduce the agglomeration phenomenon between fibers when added to mortar materials, and can significantly improve the mechanical properties and frost resistance of the fiber aerogel; further combined with ultra - high molecular weight polyethylene fiber, the probability of crack generation is significantly reduced.

[0022] Sodium tripolyphosphate dissociates into negatively charged phosphate groups after dissolving in water, adsorbs on the surface of silica sol particles, and prevents particle agglomeration through charge repulsion. When compounded with cement, sand, coarse aggregate, and ethyl acrylate emulsion, it effectively promotes size stability. Combined with the action of premix a, it significantly enhances the mechanical properties of the mortar, effectively reduces the problem of cracking, and has excellent durability.

[0023] The present invention uses a composite cellulose aerogel and ultra-high molecular weight polyethylene fibers in combination. The resulting mortar solidified product is an "organic-inorganic" mixed-phase matrix, forming an elastic interpenetrating network structure. Cement and sand are evenly distributed in the elastic network, effectively improving the high elasticity, mechanical properties, frost resistance of the mortar, and having excellent durability and good comprehensive performance. Description of the Drawings

[0024] Figure 1 It is a comparison chart of the 28-day compressive strength and 14-day tensile bond strength of the mortars obtained in Example 5 and Comparative Examples 1-2.

[0025] Figure 2 It is a comparison chart of the water retention and 28-day shrinkage rate of the mortars obtained in Example 5 and Comparative Examples 1-2.

[0026] Figure 3 It is a chart showing the change in mass loss of the test blocks made from the mortars obtained in Example 5 and Comparative Examples 1-2. Detailed Embodiments

[0027] The present invention will be further explained below in conjunction with specific embodiments.

[0028] The following manufactured sand and coarse aggregate are both purchased from LingShou NingBo Mineral Products Co., Ltd., and the fineness modulus of the manufactured sand is 2.2. The following ultra-high molecular weight polyethylene fibers are purchased from Hunan ZhongTai Special Equipment Co., Ltd., with the model ZTX99-400D, single bundle diameter 60μm, length 30mm, tensile strength 3000MPa, and ultimate elongation 2.8%. The following redispersible latex powder is purchased from Shanghai HengChuang Chemical Co., Ltd., with the model 5010N. The following silica sol particles are purchased from Wuhan JiYeSheng Chemical Co., Ltd. The following silicone defoamer is purchased from Shandong HengDa Chemical Co., Ltd. The following polycarboxylate water reducer and the following melamine water reducer are both purchased from Shandong HongQuan Chemical Technology Co., Ltd.

[0029] Example 1

[0030] A durable crack-resistant fiber mortar, the raw materials of which include: 8000g of P.O.42.5 Portland cement, 6000g of manufactured sand, 3000g of coarse aggregate, 1000g of composite cellulose aerogel, 100g of ultra-high molecular weight polyethylene fibers, 450g of redispersible latex powder, 150g of ethyl acrylate emulsion, 100g of sodium tripolyphosphate, 100g of silica sol particles, 100g of silicone defoamer, 100g of water reducer, and 8000g of water.

[0031] The water reducer is composed of polycarboxylate water reducer and melamine water reducer in a mass ratio of 3:1. The composite cellulose aerogel is prepared by the following specific operations: Add 500 g of cellulose nanofibers and 500 g of graphene oxide to 10000 g of water and ultrasonically treat for 1 h at an ultrasonic frequency of 20 kHz. Then add 500 g of acetic acid solution with a concentration of 1 mol / L and continue ultrasonically treating for 10 min. Let it stand for 5 h, perform electrospinning in an ethanol bath with an inner diameter of the electrospinning needle of 800 μm, and then freeze-dry.

[0032] The preparation method of the above-mentioned durable crack-resistant fiber mortar includes the following steps:

[0033] S1. Stir the composite cellulose aerogel, ultra-high molecular weight polyethylene fiber, and redispersible latex powder for 10 min to obtain premix a;

[0034] S2. Stir cement, manufactured sand, coarse aggregate, ethyl acrylate emulsion, sodium tripolyphosphate, silica sol particles, silicone defoamer, water reducer, and water for 10 min to obtain premix b;

[0035] S3. Mix premix a and premix b evenly.

[0036] Example 2

[0037] A durable crack-resistant fiber mortar, whose raw materials include: 12000 g of P.O.42.5 portland cement, 8000 g of manufactured sand, 5000 g of coarse aggregate, 2000 g of composite cellulose aerogel, 500 g of ultra-high molecular weight polyethylene fiber, 750 g of redispersible latex powder, 250 g of ethyl acrylate emulsion, 200 g of sodium tripolyphosphate, 500 g of silica sol particles, 200 g of silicone defoamer, 200 g of water reducer, and 16000 g of water.

[0038] The water reducer is composed of polycarboxylate water reducer and melamine water reducer in a mass ratio of 5:1. The composite cellulose aerogel is prepared by the following specific operations: Add 1500 g of cellulose nanofibers and 600 g of graphene oxide to 15000 g of water and ultrasonically treat for 2 h at an ultrasonic frequency of 30 kHz. Then add 1500 g of acetic acid solution with a concentration of 2 mol / L and continue ultrasonically treating for 20 min. Let it stand for 10 h, perform electrospinning in an ethanol bath with an inner diameter of the electrospinning needle of 1000 μm, and then freeze-dry.

[0039] The preparation method of the above-mentioned durable crack-resistant fiber mortar includes the following steps:

[0040] S1. Stir the composite cellulose aerogel, ultra-high molecular weight polyethylene fiber, and redispersible latex powder for 20 min to obtain premix a;

[0041] S2. Stir cement, manufactured sand, coarse aggregate, ethyl acrylate emulsion, sodium tripolyphosphate, silica sol particles, silicone defoamer, water reducing agent and water for 30 min to obtain premix b;

[0042] S3. Mix premix a and premix b evenly.

[0043] Example 3

[0044] A durable crack-resistant fiber mortar, the raw materials of which include: 9000 g of P.O.52.5 portland cement, 6500 g of manufactured sand, 4500 g of coarse aggregate, 1200 g of composite cellulose aerogel, 400 g of ultra-high molecular weight polyethylene fiber, 500 g of redispersible latex powder, 220 g of ethyl acrylate emulsion, 130 g of sodium tripolyphosphate, 400 g of silica sol particles, 130 g of silicone defoamer, 180 g of water reducing agent, and 10000 g of water.

[0045] The water reducing agent is composed of polycarboxylate water reducing agent and melamine water reducing agent in a mass ratio of 4.5:1. The composite cellulose aerogel is prepared by the following specific operations: Add 800 g of cellulose nanofibers and 680 g of graphene oxide to 12000 g of water, ultrasonically treat for 100 min, the ultrasonic frequency is 21 kHz, add 1600 g of acetic acid solution with a concentration of 1.2 mol / L, continue ultrasonically treat for 18 min, stand for 7 h, perform electrospinning in an ethanol bath, the inner diameter of the electrospinning needle is 900 μm, and freeze-dry.

[0046] The preparation method of the above durable crack-resistant fiber mortar includes the following steps:

[0047] S1. Stir the composite cellulose aerogel, ultra-high molecular weight polyethylene fiber, and redispersible latex powder for 18 min to obtain premix a;

[0048] S2. Stir cement, manufactured sand, coarse aggregate, ethyl acrylate emulsion, sodium tripolyphosphate, silica sol particles, silicone defoamer, water reducing agent and water for 15 min to obtain premix b;

[0049] S3. Mix premix a and premix b evenly.

[0050] Example 4

[0051] A durable crack-resistant fiber mortar, the raw materials of which include: 11000 g of P.O.52.5 portland cement, 7500 g of manufactured sand, 3500 g of coarse aggregate, 1800 g of composite cellulose aerogel, 200 g of ultra-high molecular weight polyethylene fiber, 700 g of redispersible latex powder, 180 g of ethyl acrylate emulsion, 170 g of sodium tripolyphosphate, 200 g of silica sol particles, 170 g of silicone defoamer, 120 g of water reducing agent, and 14000 g of water.

[0052] The water reducing agent is composed of polycarboxylate water reducing agent and melamine water reducing agent in a mass ratio of 3.5:1. The composite cellulose aerogel is prepared by the following specific operations: Add 1600 g of cellulose nanofibers and 520 g of graphene oxide to 16000 g of water and ultrasonically treat for 80 min, with an ultrasonic frequency of 27 kHz. Then add 800 g of acetic acid solution with a concentration of 1.8 mol / L and continue ultrasonically treat for 12 min. Let it stand for 9 h, perform electrospinning in an ethanol bath, with the inner diameter of the electrospinning needle being 900 μm, and then freeze-dry.

[0053] The preparation method of the above-mentioned durable crack-resistant fiber mortar includes the following steps:

[0054] S1. Stir the composite cellulose aerogel, ultra-high molecular weight polyethylene fiber, and redispersible latex powder for 12 min to obtain premix a;

[0055] S2. Stir cement, manufactured sand, coarse aggregate, ethyl acrylate emulsion, sodium tripolyphosphate, silica sol particles, silicone defoamer, water reducing agent, and water for 25 min to obtain premix b;

[0056] S3. Mix premix a and premix b evenly.

[0057] Example 5

[0058] A kind of durable crack-resistant fiber mortar, whose raw materials include: 10000 g of P.O.52.5 Portland cement, 7000 g of manufactured sand, 4000 g of coarse aggregate, 1500 g of composite cellulose aerogel, 300 g of ultra-high molecular weight polyethylene fiber, 600 g of redispersible latex powder, 200 g of ethyl acrylate emulsion, 150 g of sodium tripolyphosphate, 300 g of silica sol particles, 150 g of silicone defoamer, 150 g of water reducing agent, and 12000 g of water.

[0059] The water reducing agent is composed of polycarboxylate water reducing agent and melamine water reducing agent in a mass ratio of 4:1. The composite cellulose aerogel is prepared by the following specific operations: Add 1200 g of cellulose nanofibers and 600 g of graphene oxide to 14000 g of water and ultrasonically treat for 90 min, with an ultrasonic frequency of 24 kHz. Then add 1200 g of acetic acid solution with a concentration of 1.5 mol / L and continue ultrasonically treat for 15 min. Let it stand for 8 h, perform electrospinning in an ethanol bath, with the inner diameter of the electrospinning needle being 900 μm, and then freeze-dry.

[0060] The preparation method of the above-mentioned durable crack-resistant fiber mortar includes the following steps:

[0061] S1. Stir the composite cellulose aerogel, ultra-high molecular weight polyethylene fiber, and redispersible latex powder for 15 min to obtain premix a;

[0062] S2. Stir cement, manufactured sand, coarse aggregate, ethyl acrylate emulsion, sodium tripolyphosphate, silica sol particles, silicone defoamer, water reducing agent and water for 20 min to obtain premix b;

[0063] S3. Mix premix a and premix b evenly.

[0064] Comparative Example 1

[0065] A durable crack-resistant fiber mortar, the raw materials of which include: 10000 g of P.O.52.5 portland cement, 8300 g of manufactured sand, 4500 g of coarse aggregate, 300 g of ultra-high molecular weight polyethylene fiber, 750 g of redispersible latex powder, 200 g of ethyl acrylate emulsion, 150 g of silicone defoamer, 150 g of water reducing agent, and 12000 g of water.

[0066] The water reducing agent is composed of polycarboxylate water reducing agent and melamine water reducing agent in a mass ratio of 4:1. The preparation method of the above durable crack-resistant fiber mortar includes the following steps:

[0067] S1. Stir ultra-high molecular weight polyethylene fiber and redispersible latex powder for 15 min to obtain premix a;

[0068] S2. Stir cement, manufactured sand, coarse aggregate, ethyl acrylate emulsion, silicone defoamer, water reducing agent and water for 20 min to obtain premix b;

[0069] S3. Mix premix a and premix b evenly.

[0070] Comparative Example 2

[0071] A durable crack-resistant fiber mortar, the raw materials of which include: 10000 g of P.O.52.5 portland cement, 7000 g of manufactured sand, 4000 g of composite cellulose aerogel, 500 g of graphene oxide, 300 g of ultra-high molecular weight polyethylene fiber, 600 g of redispersible latex powder, 200 g of ethyl acrylate emulsion, 150 g of sodium tripolyphosphate, 300 g of silica sol particles, 150 g of silicone defoamer, 150 g of water reducing agent, and 12000 g of water.

[0072] The water reducing agent is composed of polycarboxylate water reducing agent and melamine water reducing agent in a mass ratio of 4:1. The composite cellulose aerogel is prepared by the following specific operations: Add 1200 g of cellulose nanofibers to 14000 g of water and ultrasonically treat for 90 min, the ultrasonic frequency is 24 kHz, add 1200 g of acetic acid solution with a concentration of 1.5 mol / L and continue ultrasonically treat for 15 min, let stand for 8 h, freeze spinning in an ethanol bath, the inner diameter of the spinning needle is 900 μm, and freeze drying.

[0073] The preparation method of the above durable crack-resistant fiber mortar includes the following steps:

[0074] S1. Stir the composite cellulose aerogel, graphene oxide, ultra-high molecular weight polyethylene fiber, and redispersible latex powder for 15 min to obtain premix a;

[0075] S2. Stir the cement, manufactured sand, coarse aggregate, ethyl acrylate emulsion, sodium tripolyphosphate, silica sol particles, silicone defoamer, water reducer, and water for 20 min to obtain premix b;

[0076] S3. Mix premix a and premix b evenly.

[0077] Refer to JG / T 230-2007 "Ready-mixed Mortar" to measure the 28-day compressive strength, 14-day tensile bond strength, water retention, and 28-day shrinkage rate of the mortar obtained in Example 5 and Comparative Examples 1-2.

[0078] As Figure 1 and Figure 2 shown, the 28-day compressive strength, 14-day tensile bond strength, and water retention of the mortar obtained in Example 5 are the highest, while the 28-day shrinkage rate is the smallest, being superior to Comparative Examples 1-2 (P < 0.05).

[0079] Refer to GB / T 50082-2009 "Standard Test Method for Long-term Performance and Durability of Ordinary Concrete" and JGJ / T70-2009 "Test Methods for Basic Properties of Building Mortar" to prepare test blocks and conduct slow freeze-thaw cycle test on them. After the test blocks are formed and demolded, they are taken out after curing in the standard curing room for 28 d, and then the test blocks are immersed in water. After 1 d of immersion, the test blocks are taken out of the water, and the surface water on the test blocks is wiped dry with a wet cloth and their wet weights are measured. Then the test blocks are placed in the specimen box of the freeze-thaw cycle testing machine for freeze-thaw cycle experiments. The wet weight of the test blocks is measured every 5 cycles, and the mass loss of the test blocks is calculated.

[0080] As Figure 3 shown, the mass loss of the test blocks prepared with the mortar obtained in Example 5 is the least, being superior to Comparative Examples 1-2 (P < 0.05).

[0081] The applicant believes that: This is because the present invention utilizes the compounding of cellulose nanofibers and graphene oxide. With the cooperation of acetic acid, the combination of the two has excellent stability. During the freezing process, a porous three-dimensional network structure is formed through the ice crystal template method. It not only has the characteristics of controllable pore size and orderly pore arrangement, but also can rebound after being compressed, with good elasticity. At the same time, it is compounded with polymer powder, which can significantly reduce the agglomeration phenomenon between fibers when added to mortar materials, and can significantly improve the mechanical properties and frost resistance of the fiber aerogel; further combined with ultra-high molecular weight polyethylene fibers, the probability of crack generation is significantly reduced. The present invention utilizes sodium tripolyphosphate adsorbed on the surface of silica sol particles to prevent particle agglomeration through charge repulsion, and is compounded with cement, sand, coarse aggregate, and ethyl acrylate emulsion, effectively promoting dimensional stability. With the action of premix a, the mechanical properties of the mortar are significantly enhanced, and the problem of cracking is effectively reduced, with excellent durability. At the same time, the composite cellulose aerogel is compounded with ultra-high molecular weight polyethylene fibers, and the obtained mortar solidified product is an "organic-inorganic" mixed-phase matrix, forming an elastic interpenetrating network structure. Cement and sand are evenly distributed in the elastic network, effectively improving the high elasticity, mechanical properties, and frost resistance of the mortar, with excellent durability and good comprehensive performance.

[0082] The above is only the preferred specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A durable crack-resistant fiber mortar, characterized in that: The raw materials include, by mass: 80-120 parts of cement, 60-80 parts of sand, 30-50 parts of coarse aggregate, 10-20 parts of composite cellulose aerogel, 1-5 parts of ultra-high molecular weight polyethylene fiber, 4.5-7.5 parts of polymer powder, 1.5-2.5 parts of ethyl acrylate emulsion, 1-2 parts of sodium tripolyphosphate, 1-5 parts of silica sol particles, 1-2 parts of defoaming agent, 1-2 parts of water reducing agent, and 80-160 parts of water; The raw materials of the composite cellulose aerogel include: cellulose nanofibers and graphene oxide, and the mass ratio of the cellulose nanofibers to the graphene oxide is 1-5:1-2.

2. The durable crack-resistant fiber mortar according to claim 1, characterized in that: The cement is PO42.5 silicate cement and / or PO52.5 silicate cement.

3. The durable crack-resistant fiber mortar according to claim 1, characterized in that: The polymer powder is a redispersible latex powder.

4. The durable crack-resistant fiber mortar according to claim 1, characterized in that: The fineness modulus of sand is 2.0-2.

5.

5. The durable crack-resistant fiber mortar according to claim 1, characterized in that: Water reducing agents include: Polycarboxylate water reducer and melamine water reducer.

6. The durable crack-resistant fiber mortar according to claim 5, characterized in that: The mass ratio of polycarboxylate water reducer to melamine water reducer is 3-5:

1.

7. The durable crack-resistant fiber mortar according to claim 1, characterized in that: The composite cellulose aerogel is prepared by the following specific operation: cellulose nanofibers and graphene oxide are added to water and ultrasonically treated for 1-2 hours, acetic acid solution is added and ultrasonically treated for 10-20 minutes, and the mixture is allowed to stand for 5-10 hours, followed by freeze spinning in an ethanol bath and freeze drying.

8. The durable crack-resistant fiber mortar according to claim 7, characterized in that: The concentration of the acetic acid solution is 1-2 mol / L.

9. The durable crack-resistant fiber mortar according to claim 7, characterized in that: The ultrasonic frequency is 20-30kHz.

10. A method for preparing the durable crack-resistant fiber mortar according to any one of claims 1 to 9, characterized in that: The steps include: S1, stirring the composite cellulose aerogel, ultra-high molecular weight polyethylene fiber, and polymer powder for 10-20 minutes to obtain a premix a; S2, mixing cement, sand, coarse aggregate, ethyl acrylate emulsion, sodium tripolyphosphate, silica sol particles, defoamer, water reducer and water for 10-30 minutes to obtain premix b; S3, mix premix a and premix b evenly.

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